In many telecommunication systems, communications networks are used to exchange messages among several interacting spatially-separated devices. Networks may be classified according to geographic scope, which could be, for example, a metropolitan area, a local area, or a personal area. Such networks would be designated respectively as a wide area network (WAN), a metropolitan area network (MAN), a local area network (LAN), or a personal area network (PAN). Networks also differ according to switching techniques and/or routing techniques used to interconnect various network nodes and devices (e.g. circuit switching vs. packet switching), a type of physical media employed for transmission (e.g. wired vs. wireless), and a set of communication protocols used (e.g. Internet protocol suite, Synchronous Optical Networking (SONET), Ethernet, etc.).
Wireless networks are often preferred when network elements are mobile and thus have dynamic connectivity needs, or if a network architecture is formed in an ad-hoc, rather than fixed, topology. Wireless networks employ intangible physical media in an unguided propagation mode using electromagnetic waves in radio frequency bands, microwave frequency bands, infra-red frequency bands, optical frequency bands, etc. Wireless networks advantageously facilitate mobility and rapid field deployment when compared to fixed, wired networks. However, wireless communication requires significant active resource management among network user devices and higher levels of mutual coordination and cooperation for compatible spectrum utilization as compared to wired communication.
In a single basic service set (BSS), a first station (STA) and a second STA may both be associated with the same access point (AP) and communicate via the AP. Within the single BSS, the first STA may establish a direct link for direct communication (e.g., not via the AP) with the second STA. Prior to establishing the direct link, all messages between the first STA and the second STA are routed via the AP of the single BSS. Because the first STA and the second STA are in the same BSS (i.e., associated with the single AP), both the first STA and the second STA communicate with the single AP using the same communication channel(s).
In an extended service set (ESS), a first AP associated with a first BSS may be connected to a second AP associated with a second BSS. The connection may be a bridged connection (i.e., a layer 2 connection). A first STA in the first BSS may communicate with a second STA of the second BSS via the first AP and the second AP. In the ESS, the first STA of the first BSS is generally unaware of the communication channel used by the second STA in the second BSS. Thus, direct link procedures applied to two STAs in the same BSS may not be sufficient to establish a direct link between two STAs in different BSSs at least because the first STA and the second STA are not associated and communicating with a single AP using the same communication channel(s).